While the pulmonary damage resulting from acute, short-term exposure to components of photochemical smog have been well characterized biochemically, morphologically and physiologically in adults, very little information is available concerning the mechanisms by which the respiratory system adapts to continual insult over the lifetime of an organism. The goal of this work area will be to elucidate the nature of the interactions between the cells of the growing lung and environmental irritants. The emphasis will be on pulmonary reactions occurring over the entire life span of the organism (prenatal to death) in response to gases at realistic environmental concentrations. The first phase is to characterize the normal cellular events during prenatal and early postnatal development of the mammalian lung of a non-human primate (M. mulatta). Once the usefulness of the rhesus monkey as a model for studies of pollutant effects on lung development has been established, specific protocols will be developed to evaluate pollutant effects on alveolarization, cellular maturation and overall lung growth and repair phenomena.